The present invention relates generally to the field of guidewires and, more specifically, to the field of pressure-sensing guidewires used in intravascular procedures. Still more specifically, the present invention relates to a system and method for extending the length of pressure-sensing guidewires during intravascular procedures.
Guidewires are used in various medical procedures to position medical devices at desired locations within a patient""s vascular system. Guidewires are inserted into the patient""s vasculature and steered or maneuvered within a guide catheter to a location of interest. Once in place, the guidewire provides the means to place a device, such as a catheter, within the patient""s vasculature at the location of interest.
Pressure-sensing guidewires are also utilized for medical procedures. Typically, pressure-sensing guidewires comprise a hollow wire with at least one opening disposed towards the distal end of the wire. Pressure is communicated through the opening and down the lumen defined by the wire to the proximal end of the wire. The proximal end of the wire is then connected to a transducer for measuring the intravascular pressure communicated through the guidewire. Knowledge of the intravascular pressure at specific locations within a vessel or artery is important in determining whether angioplasty should be performed at all.
In angioplasty a dilatation catheter having an inflatable balloon structure is used to compress an occlusion or stenosis against the sides of a vessel, thereby permitting circulation to be reestablished. After the location of the occlusion is identified, a pressure-sensing guidewire is inserted into the patient""s artery and maneuvered or steered to the location of the restriction. Maneuvering of the guidewire is facilitated by fluoroscopy which allows the physician to observe the movement of the guidewire. The guidewire generally comprises a radiopaque material to enhance viewing. Preferably, vascular pressure both proximal and distal to the occlusion is measured to determine if treatment is necessary.
If angioplasty is to be performed, a dilatation catheter is inserted over the guidewire so that its working segment is located adjacent the occlusion. During an angioplasty procedure, the dilatation catheter balloon is inflated to open the restriction, and then is subsequently removed along with the guidewire. However, instances sometimes arise which prevent the physician from completing the procedure. Sometimes a different size balloon is required further to dilate the vascular occlusion, or another device or other type of catheter is needed to remove plaque material. A guidewire extension system is needed when the catheter, or other such device, has to be removed and replaced with another device or catheter.
In the usual procedure to exchange catheters, the guidewire is removed from the patient, leaving the catheter in the vascular system. An exchange wire is inserted through the catheter and the catheter is removed, leaving the exchange wire in place. The new catheter is inserted over the exchange wire and the exchange wire removed and replaced with the guidewire.
It is desirable to keep the guidewire in the patient""s vasculature instead of withdrawing the guidewire as described above and replacing it with a longer guidewire for various reasons. One reason is that the initial placement of the guidewire requires extensive, time consuming, manipulation. Removal and repositioning of the guidewire is equally time consuming. It is also important that once the guidewire has been steered to a position across an occlusion, that the position not be lost by removal of the guidewire. Guidewires that are removed from a crossed occlusion may induce spontaneous restriction or closure making repositioning of the guidewire difficult.
In those cases where a catheter exchange is required, it is desirable to remove the catheter over the guidewire, leaving the guidewire positioned in the patient. However, to permit a catheter exchange, a guidewire over which a catheter is to be exchanged must be long enough to allow the physician to grip a portion of the wire as the catheter is being withdrawn over the guidewire. This requires the guidewire to be long enough to provide an external portion beyond the catheter in addition to the guidewire portion remaining in the patient. Typically, the guidewire must be 110-180 cm longer than the catheter in order for an exchange to be executed.
However, guidewires, and, more specifically, hollow pressure-sensing guidewires that are too long have inferior handling characteristics, thereby making it more difficult to steer and maneuver the guidewire. The added length needed for an exchange also causes the proximal end of the guidewire to be exposed from the patient and possibly being non-sterile and difficult for the physician to maneuver in the procedure. It is for these reasons that guidewires are typically only slightly longer than balloon catheters, e.g., 20-50 centimeters longer, and that a much longer exchange wire is used only with exchange procedures.
A dilatation catheter has a shaft length in the range of about 120 cm to about 150 cm. A suitable guidewire for such a catheter would have a length in the range of about 150 cm to about 180 cm and a suitable exchange guidewire would have a length in the range of about 260 cm to about 330 cm. As can be imagined from the above, utilization of an exchange guidewire in a catheter exchange procedure is complicated and time consuming.
Coupling or connecting a second length of wire, sometimes called an extension wire or secondary wire, to the exposed, proximal end of a positioned guidewire is known. The secondary wire length should be sufficient to allow the catheter to be withdrawn while leaving the primary guidewire positioned within the patient""s coronary or peripheral vasculature. Various approaches have been suggested for effecting the attachment of an extension wire to a guidewire.
The prior art guidewire extension systems all have one or more drawbacks. Some are difficult or tedious or intricate to engage and disengage. Others simply do not disengage. While frictional engagement overcomes the disadvantages of crimping, disengagement may occur too easily. Some connector systems are difficult or expensive to build, especially in smaller diameter sizes.
Further, none of the above-described guidewire extension systems are designed to be used with pressure-sensing guidewires. That is, none of the extension systems described above are designed to be used with a hollow pressure-sensing guidewire. They are all intended to be used and designed for a solid guidewire structure.
Because of the emergence of pressure-sensing guidewires and the importance of measuring vascular pressure at points both proximal and distal to an occlusion prior to the performance of angioplasty procedure, an improved extension system for pressure-sensing guidewires is desired.
The present invention overcomes the deficiencies of the prior art by providing a pressure-sensing guidewire assembly that includes an extension member. The guidewire assembly comprises a pressure-sensing guidewire comprising an elongated tubular member comprising a proximal end, a distal end and a lumen extending between the proximal and distal ends. The guidewire further comprises at least one opening disposed adjacent the distal end for providing fluid communication to the lumen. The assembly further comprises an elongated extension member detachably connected to the proximal end of the elongated tubular member.
In another embodiment, a method for extending the length of a pressure-sensing guidewire is provided wherein the guidewire comprises an elongated tubular member comprising a proximal end, a distal end and a lumen extending between the proximal and distal ends. The guidewire further comprises at least one opening disposed adjacent the distal end for providing fluid communication to the lumen. The method comprises the step of connecting an elongated extension member to the proximal end of the tubular member.